| 摘要 |
A pipeline pig comprises a body and at least one flexible annular outwardly extending seal on and around the body for sealingly contacting a pipeline interior wall under differential fluid pressure whereby to propel the pig along the pipeline. The pig also comprises fluid bypass duct means through the body and resilient frictional means on and extending from the body adapted to contact the pipeline interior wall and exert a drag on the pig. An adjustable bypass flow control means is provided which is adapted to regulate fluid flow through the duct means and thus the speed of the pig.
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